\begin{tikzpicture}
    \tkzDefPoints{0/0/B,  4/0/C,  1.6/2.5/A,  2.6/0/D}

    \tkzDrawPolygon(A,B,C)
    \tkzDrawSegment(A,D)
    \tkzLabelPoints[above](A)
    \tkzLabelPoints[left](B)
    \tkzLabelPoints[right](C)
    \tkzLabelPoints[below](D)
\end{tikzpicture}

